Storage media, such as disks in hard drives, should be backed up regularly to protect against data loss or corruption. There are many known systems and methods for backing up computers. Backup types include a full backup, which is a copy of all files associated with a specified machine or system, a differential backup, which is a backup or copy of the files that have changed since the last full backup, and an incremental backup, which is a backup or copy of files that have changed since the previous incremental backup or full backup, whichever is most recent. The terms differential backup and incremental backup are sometimes used interchangeably. Well-known methods for personal computers involve the use of file modification time or archive bits, which are attributes of a file system record. A file that has been changed since a previous backup has an updated modification time and archive bit set. Once the file is copied, for a backup, the archive bit may be cleared. Determining which files to copy requires looking through the entire file system records to find which files have an updated modification date or archive bits set. For a single user computer of modest storage size, this is not a major burden. However, for enterprise systems, especially those employing virtualization, looking through all of the file system records to determine which files have modification date has been updated or set archive bits is a time-consuming task. Also, there are reliability issues, since the archive bits may be user accessible.
In one embodiment, A backup systems for virtual environments will generate a map all of the files and data within a virtual environment and then back up the map and the data according to the map. This methodology is used for full backups, incremental backups and differential backups. A sequential scan of the file system indexes of every file system within the virtual environment is performed, in order to generate the map. In the case of an incremental or a differential backup, the generation of the map can take more time than the backup of the actual data. Therefore, there is a need in the art for a solution which overcomes the drawbacks described above.